Fig. 1.

Secondary xylem structure differs greatly throughout the plant body of large woody plants as demonstrated in the structure of xylem within excavated mature Populus tristis trees. Distal stems (A) contain vary narrow vessels, with vessel diameter widening considerably in basal sections of the shoot within the bole (B). Older wide roots contain the widest vessel diameters found within the plant body (C), and root vessel diameters taper towards root apices (D) but still remain much wider than vessels found within the shoot. The micrographs and tree diagram are previously unpublished and show tree and xylem micrographs from samples collected as part of Jacobsen et al. (2018). Lines from micrographs to locations on the tree diagram indicate the approximate sample location of the corresponding xylem tissue within the tree body. All micrographs were taken at the same magnification; scale bar = 200 µm.